Java中的 ShortBuffer compact() 方法及示例

Java.nio.ShortBuffer类的compact()方法用于压缩给定的缓冲区。缓冲区的当前位置与其限制之间的短路（如果有）被复制到缓冲区的开头。也就是说，索引 p = position() 处的空头被复制到索引 0，索引 p + 1 处的空头被复制到索引 1，依此类推，直到索引 limit() – 1 处的空头被复制到索引 n =限制（） - 1 - 页。然后将缓冲区的位置设置为 n+1，并将其限制设置为其容量。标记（如果已定义）将被丢弃。缓冲区的位置设置为复制的短裤的数量，而不是零，因此调用此方法后可以立即调用另一个相对 put 方法。

语法：

public abstract ShortBuffer compact()

返回值：此方法返回与此缓冲区内容相同的新 ShortBuffer 。

异常：此方法抛出ReadOnlyBufferException ，如果此缓冲区是只读的。

下面的程序说明了compact()方法：

程序 1 ：

// Java program to demonstrate
// compact() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the ShortBuffer
        int capacity = 10;
  
        // Creating the ShortBuffer
  
        // creating object of shortbuffer
        // and allocating size capacity
        ShortBuffer sb = ShortBuffer.allocate(capacity);
  
        // putting the value in shortbuffer
        sb.put((short)856);
        sb.put((short)961);
        sb.put((short)54);
  
        // print the ShortBuffer
        System.out.println("Original ShortBuffer: "
                           + Arrays.toString(sb.array()));
  
        System.out.println("Position: " + sb.position());
  
        System.out.println("limit: " + sb.limit());
  
        // Creating a compacted ShortBuffer of same ShortBuffer
        // using compact() method
        ShortBuffer shortBuffer = sb.compact();
  
        // print the ShortBuffer
        System.out.println("\nCompacted ShortBuffer: "
                           + Arrays.toString(shortBuffer.array()));
  
        System.out.println("Position: " + shortBuffer.position());
  
        System.out.println("limit: " + shortBuffer.limit());
  
        // putting the value in compacted shortbuffer
        shortBuffer.put((short)961);
  
        // print the ShortBuffer
        System.out.println("\nUpdated Compacted ShortBuffer: "
                           + Arrays.toString(shortBuffer.array()));
        System.out.println("Position: " + shortBuffer.position());
        System.out.println("limit: " + shortBuffer.limit());
    }
}

输出：

Original ShortBuffer: [856, 961, 54, 0, 0, 0, 0, 0, 0, 0]
Position: 3
limit: 10

Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Position: 7
limit: 10

Updated Compacted ShortBuffer: [0, 0, 0, 0, 0, 0, 0, 961, 0, 0]
Position: 8
limit: 10

程序2：演示ReadOnlyBufferException。

// Java program to demonstrate
// compact() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the ShortBuffer
        int capacity = 10;
  
        // Creating the ShortBuffer
        try {
  
            // creating object of ShortBuffer
            // and allocating size capacity
            ShortBuffer sb = ShortBuffer.allocate(capacity);
  
            // putting the value in floatbuffer
            sb.put((short)856);
            sb.put((short)961);
            sb.put((short)6010);
            sb.rewind();
  
            // Creating a read-only copy of ShortBuffer
            // using asReadOnlyBuffer() method
            ShortBuffer sb1 = sb.asReadOnlyBuffer();
  
            // print the ReadOnlyBuffer
            System.out.print("ReadOnlyBuffer ShortBuffer: ");
            while (sb1.hasRemaining())
                System.out.print(sb1.get() + ", ");
            System.out.println("");
  
            // print the Position of ShortBuffer sb
            System.out.println("\nPosition: " + sb.position());
  
            // print the Limit of ShortBuffer fb
            System.out.println("\nlimit: " + sb.limit());
  
            // Creating a compacted ShortBuffer of same ReadOnlyBuffer
            // using compact() method
            System.out.println("\nTrying to compact the ReadOnlyBuffer sb1");
  
            ShortBuffer floatBuffer = sb1.compact();
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws " + e);
        }
    }
}

输出：

ReadOnlyBuffer ShortBuffer: 856, 961, 6010, 0, 0, 0, 0, 0, 0, 0, 

Position: 0

limit: 10

Trying to compact the ReadOnlyBuffer sb1
Exception throws java.nio.ReadOnlyBufferException